Spark advance/retard control servo for an internal combustion engine

ABSTRACT

A dual diaphragm distributor actuator has a one piece ring member that separates the diaphragms and constitutes a stop to limit movement of one of the diaphragms in both spark advance and retard directions, and the other diaphragm in a spark retard direction, the stop having axially separate sets of radially depending abutments engaged alternately by a control part extending radially from the one diaphragm so as to be straddled by the abutments, the sets having circumferentially spaced arcuate parts alternating circumferentially with the parts of the other set to form a bayonet type assembly of the abutments and control part.

1451 Apr. 1972 .1 States 'flrowet" [54] SPARK ADVANQE/RETA QUNTRflL3,352,209 11/1967 Cripe 2,837,119 6/1958 Schwarz et a1.... 3,096,6897/1963 SERVO FOR AN INTERNAL COMBUSTION ENGINE [72] lnventorz XXXQ 999499 ///9 227. u 999 3,397,621 8/1968 Groves................

Primary Examiner-Edgar W. Geoghegan Assistant Examiner-Leslie .1. Payne[73] Assignee:

[22] Filed:

Attorney-John R. Faulkner and Robert E. McCollum ABSTRACT spaced arcuateparts alternating circumferentially with the [56] References cued partsof the other set to form a bayonet type assembly of the UNITED STATESPATENTS abutments and control part.

.92/48 x 4 Claims, 4 Drawing Figures SPARK ADVAN CE/RETARD CONTROL SERVOFOIR AN INTERNAL COMBUSTION ENGINE This invention relates to sparkadvance/retard devices for distributors of spark ignition internalcombustion engines.

In a known device now in use, shown and described in US. Pat. No.3,385,275, a rod is movable to advance or retard the spark; a firstdiaphragm is fixed to the rod and forms a wall of a first chamber; thefirst chamber is subject to the pressure in the induction systemadjacent to the engine throttle valve; a stop is movable between firstand second positions to control the limits of axial movement of the rod;there is a second diaphragm to which the movable stop is fixed; thesecond diaphragm forms a wall of a second chamber and is subject to thepressure in the induction system downstream of the throttle valve; and,each of the diaphragms is resiliently biased to urge them in theopposite direction to that in which they are respectively urged byvacuum in their respective chambers.

In such a device, a two part spacer is located between the diaphragms tohold the diaphragms in contact with the walls of their respectivechambers; and, one part of the spacer has an abutment that limitsmovement of the stop in one direction while the other part of the spacerhas an abutment that limits movement of the stop in the other direction.

The two part spacer increases the cost of the device and also involvesan extra assembly operation. This invention provides a construction thatreduces the cost of the device and provides an easier assemblyoperation.

According to this invention, a one piece annular spacer is locatedbetween the diaphragms to hold or anchor the diaphragms in contact withthe walls of their respective chambers; and, the spacer has abutments tolimit movement of the movable stop, the abutments consisting ofcircumferentially and axially separated parts that project radiallyinwardly and form with projections on the stop a bayonet type joint.

Other features, advantages and objects of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawings illustrating a preferred embodiment thereof,wherein;

FIG. 1 is a cross-sectional view through a device embodying theinvention;

FIG. 2 is an end view of part of the device of FIG. 1;

FIG. 3 is a cross-sectional view of the part shown in FIG. 2; and,

FIG. 4 is an end view ofa part shown in FIG. 1.

The device comprises a left hand casing 1, a right hand annular casing3, and a spacer 5 between flanges on the casings 1 and 3. A firstdiaphragm 7 is clamped between the spacer 5 and the flange of the casing1; while a second annular diaphragm 8 is clamped between the spacer 5and the flange of the casing 3.

An assembly of a cup-shaped member 9, an element 11, and a rod 13 isfixed to the center of the first diaphragm 7. A spring 15 is compressedbetween the casing 1 and cup-shaped member 9 to force the diaphragm 7and rod 13 rightwardly. The rod 13 projects through the central openingin the casing 3 and is connected to the distributor, and as it is movedaxially to the left or right, it advances or retards the ignition. Thediaphragm 7 closes the open end of the casing l to form a vacuum chamberwhich is connected by a pipe, not shown, to the induction system at apoint upstream of and adjacent the periphery of the throttle valve, whenit is in its engine idle speed position.

The inner radial edge of the diaphragm 8 is clamped between a turnedover lip 19 at the inner side of the casing 3. An assembly comprising acup-shaped member 21 and a control member 23 is attached to thediaphragm 8 by three fasteners 25. A coil spring 27 is compressedbetween the base of the casing 3 and the member 21 to force thediaphragm 8 towards the left in FIG. 1. The diaphragm 8 seals the end ofthe casing 3 so that it forms a second vacuum chamber. This chamber isconnected by a pipe 29 to the induction system downstream of thethrottle valve.

The member 23 is annular and has an inner flange 31 and an outer flange33. The inner flange 31 is engaged by the member 1 1 attached to thediaphragm 7. The outer flange 33 alternately engages axially spacedabutments 37a and 37b that straddle flange 33 and are integral with andproject inwardly from the spacer 5. The member 23 and abutments integralwith the spacer 5 form a bayonet type joint.

. The outer flange 33 of stop 23 consists of three arcuate projections35 (FIG. 4); the radial extent of each one is between the radialextentsof the inwardly projecting sections 370 and b. The assembly of thediaphragm 8, stop 23 and cup-shaped member 21 can, therefore, be movedaxially towards the spacer 5 with the projections 35 passing betweenadjacent sections 37. As stated above, adjacent sections 37 a and b areaxially spaced (FIG. I); thus section 37a is closer to the diaphragm 7than the adjacent section 37b. When the projections 35 (FIG. A1) areaxially positioned between adjacent sections 37a and 37b, andcircumferentially between adjacent abutments 37a, the assembly of thediaphragm 8, stop 23 and cup-shaped member 21 can be rotatedcircumferentially until each projection 35 overlaps both a section 37aand a section 37b. The axial distance that the projections 35 and hencethe stop 23 can move is thus determined by the axial distance betweenadjacent sections 37a and 37b.

As best seen in FIG. 2, the abutments 37a and 37b consist of threearcuate projections 37a circumferentially spaced equally from oneanother and alternating circumferentially with three spaced arcuateprojections 37b. The abutments a and b depend radially from oppositeaxial sides of spacer 5, with 37a extending radially inwardly fartherthan 37b.

It will be seen that the invention provides a spacer 5 formed in onepiece and formed with the abutments 37a and 37b and stop 21 as a bayonettype joint. The movement of diaphragm 8 in a leftward or spark advancedirection is limited by the stop 37a, and in a rightward or spark retarddirection by the stop 37b. The diaphragm 7 can move freely in a leftwardadvance direction, and is controlled in its rightward retard movement byabutment against the movable stop 23.

- I claim:

1. A fluid motor assembly comprising, a housing, a pair of flexiblediaphragm members each mounted in said housing for an independentmovement relative to the other and each with said housing defining adifferent vacuum chamber, means connecting each of said chambers to aseparate source of fluid varying from a maximum essentially atmosphericpressure level to a minimum sub-atmospheric pressure or vacuum level forreciprocable movement of each of said members as a function of thechanges in vacuum acting thereon, spring means biasing each of saiddiaphragm members towards the other, movable actuating means connectedto a first one of said diaphragm members for movement therewith, meanson said first diaphragm member engageable at times with the other secondone of said members upon movement of said first member in one directionfor limiting the movement of said first member in said one direction ina variable manner as a function of the position of said second member,and stop means in the path of movement of said second member providing alimited movement of said latter diaphragm member, said stop meanscomprising a one piece ring-like member having radially inwardlyextending abutment members that are axially spaced with respect to eachother and project into the path of movement of said second member foralternate engagement by the second member.

2. An assembly as in claim 1, each of said abutment members comprising aset of circumferentially spaced portions.

3. An assembly as in claim 2, said axially spaced sets having theirportions circumferentially alternated with the circumferentially spacedportions of the other set to form a bayonet type assembly.

4. An assembly as in claim 2, including guide means on said seconddiaphragm member cooperable with said stop means to limit movement inopposite directions of said second diaphragm, said guide means extendingradially between the inner and outer radial portions of said abutmentportions.

1. A fluid motor assembly comprising, a housing, a pair of flexible diaphragm members each mounted in said housing for an independent movement relative to the other and each with said housing defining a different vacuum chamber, means connecting each of said chambers to a separate source of fluid varying from a maximum esSentially atmospheric pressure level to a minimum sub-atmospheric pressure or vacuum level for reciprocable movement of each of said members as a function of the changes in vacuum acting thereon, spring means biasing each of said diaphragm members towards the other, movable actuating means connected to a first one of said diaphragm members for movement therewith, means on said first diaphragm member engageable at times with the other second one of said members upon movement of said first member in one direction for limiting the movement of said first member in said one direction in a variable manner as a function of the position of said second member, and stop means in the path of movement of said second member providing a limited movement of said latter diaphragm member, said stop means comprising a one piece ring-like member having radially inwardly extending abutment members that are axially spaced with respect to each other and project into the path of movement of said second member for alternate engagement by the second member.
 2. An assembly as in claim 1, each of said abutment members comprising a set of circumferentially spaced portions.
 3. An assembly as in claim 2, said axially spaced sets having their portions circumferentially alternated with the circumferentially spaced portions of the other set to form a bayonet type assembly.
 4. An assembly as in claim 2, including guide means on said second diaphragm member cooperable with said stop means to limit movement in opposite directions of said second diaphragm, said guide means extending radially between the inner and outer radial portions of said abutment portions. 